The invention is in the field of electronic circuits for starting and ballasting high-pressure, high-intensity arc lamps. An example of one of many such type lamps is disclosed in U.S. Pat. No. 3,305,289 to Elmer Fridrich. Such lamps operate in three modes:
(1) Starting mode (comprising a glow breakdown mode followed by a glow-to-arc transition) in which a relatively high value of a-c or d-c starting voltage is applied across the lamp's electrodes to first condition the lamp's gases into suitable ionized condition for striking a glow, followed by a time period up to a minute or so to cause a transition into an arc between the lamps's electrode tips; PA0 (2) Operating mode, in which the lamp's arc discharge generates desired light output and a relatively low or moderate voltage occurs across the lamp's electrodes in response to a suitable arc discharge current as established by the ballast circuit; and PA0 (3) Hot Restart mode, in which the lamp's arc discharge fails or extinguishes for some reason such as a momentary interruption of its current supply. If the arc extinguishes, the lamp must be permitted to cool for up to a minute or more before the arc can be restarted by the normal starting voltage.
In contrast to the foregoing, low-pressure lamps such as fluorescent lamps can be started with a single short-duration relatively low voltage pulse, and furthermore do not have a hot restart problem.
Numerous circuits have been devised for starting, operating, and hot-restarting high pressure arc lamps. Some examples are disclosed in U.S. Pat. No. 4,060,751 to Thomas E. Anderson, which discloses a variable frequency L-C resonant starting inverter circuit which increases the starting voltage until the arc is established in the lamp and the inverter circuit then functions as the operating ballast; and in U.S. Pat. No. 4,048,539 to Walker and Kornrumpf which discloses a circuit having a starting transformer secondary in series with the arc lamp to provide starting and hot-restarting of the lamp.
In a typical prior-art arc lamp circuit in which some or all of the starting transformer inductance remains in the series ballast circuit for operating the lamp, the series ballast inductance must have wire of sufficient cross-section diameter to safely pass the operating current of the arc lamp, which thus requires a starting transformer of larger size, greater weight, and greater heat-dissipation capability, than would be required if the starting transformer functioned only for starting and not for ballasting.